HP OpenVMS Systems Documentation

OpenVMS Cluster Systems

For process execution to resume, the cluster votes total must be
restored to a value greater than or equal to the cluster quorum value.
Often, the required votes are added as computers join or rejoin the
cluster. However, waiting for a computer to join the cluster and
increasing the votes value is not always a simple or convenient remedy.
An alternative solution, for example, might be to shut down and reboot
all the computers with a reduce quorum value.

After the failure of a computer, you may want to run the Show Cluster
utility and examine values for the VOTES, EXPECTED_VOTES, CL_VOTES, and
CL_QUORUM fields. (See the OpenVMS System Management Utilities Reference Manual for a complete description of
these fields.) The VOTES and EXPECTED_VOTES fields show the settings
for each cluster member; the CL_VOTES and CL_QUORUM fields show the
cluster votes total and the current cluster quorum value.

To examine these values, enter the following commands:

$ SHOW CLUSTER/CONTINUOUS
COMMAND> ADD CLUSTER

Note: If you want to enter SHOW CLUSTER commands
interactively, you must specify the /CONTINUOUS qualifier as part of
the SHOW CLUSTER command string. If you do not specify this qualifier,
SHOW CLUSTER displays cluster status information returned by the DCL
command SHOW CLUSTER and returns you to the DCL command level.

If the display from the Show Cluster utility shows the CL_VOTES value
equal to the CL_QUORUM value, the cluster cannot survive the failure of
any remaining voting member. If one of these computers shuts down, all
process activity in the cluster stops.

Use the DCL command SET CLUSTER/EXPECTED_VOTES to adjust the cluster
quorum to a value you specify.

If you do not specify a value, the operating system calculates an
appropriate value for you. You need to enter the command on only one
computer to propagate the new value throughout the cluster. When you
enter the command, the operating system reports the new value.

Suggestion: Normally, you use the SET
CLUSTER/EXPECTED_VOTES command only after a computer has left the
cluster for an extended period. (For more information about this
command, see the OpenVMS DCL Dictionary.)

Example: For example, if you want to change expected
votes to set the cluster quorum to 2, enter the following command:

$ SET CLUSTER/EXPECTED_VOTES=3

The resulting value for quorum is (3 + 2)/2 = 2.

Note: No matter what value you specify for the SET
CLUSTER/EXPECTED_VOTES command, you cannot increase quorum to a value
that is greater than the number of the votes present, nor can you
reduce quorum to a value that is half or fewer of the votes present.

When a computer that previously was a cluster member is ready to
rejoin, you must reset the EXPECTED_VOTES system parameter to its
original value in MODPARAMS.DAT on all computers and then reconfigure
the cluster according to the instructions in Section 8.6. You do not
need to use the SET CLUSTER/EXPECTED_VOTES command to increase cluster
quorum, because the quorum value is increased automatically when the
computer rejoins the cluster.

Use the IPC Q command to recalculate the quorum.

Refer to the OpenVMS System Manager's Manual, Volume 1: Essentials for a description of the Q command.

Sometimes performance issues involve monitoring and tuning applications
and the system as a whole. Tuning involves collecting and reporting on
system and network processes to improve performance. A number of tools
can help you collect information about an active system and its
applications.

The following table briefly describes the SHOW commands available with
the OpenVMS operating system. Use the SHOW DEVICE commands and
qualifiers shown in the table.

Command

Purpose

SHOW DEVICE/FULL

Shows the complete status of a device, including:

Whether the disk is available to the cluster

Whether the disk is MSCP served or dual ported

The name and type (VAX or HSC) of the primary and secondary hosts

Whether the disk is mounted on the system where you enter the
command

The systems in the cluster on which the disk is mounted

SHOW DEVICE/FILES

Displays a list of the names of all files open on a volume and their
associated process name and process identifier (PID). The command:

Lists files opened only on this node.

Finds all open files on a disk. You can use either the SHOW
DEVICE/FILES command or SYSMAN commands on each node that has the disk
mounted.

SHOW DEVICE/SERVED

Displays information about disks served by the MSCP server on the node
where you enter the command. Use the following qualifiers to customize
the information:

/HOST displays the names of processors that have devices online
through the local MSCP server, and the number of devices.

/RESOURCE displays the resources available to the MSCP server,
total amount of nonpaged dynamic memory available for I/O buffers, and
number of I/O request packets.

/COUNT displays the number of each size and type of I/O operation
the MSCP server has performed since it was started.

/ALL displays all of the information listed for the SHOW
DEVICE/SERVED command.

The SHOW CLUSTER command displays a variety of information about the
OpenVMS Cluster system. The display output provides a view of the
cluster as seen from a single node, rather than a complete view of the
cluster.

Reference: The OpenVMS System Management Utilities Reference Manual contains complete
information about all the SHOW commands and the Show Cluster utility.

Compaq Availability Manager and DECamds are real-time monitoring,
diagnostic, and correction tools used by system managers to improve the
availability and throughput of a system. Availability Manager runs on
OpenVMS Alpha or on a Windows node. DECamds runs on both OpenVMS VAX
and OpenVMS Alpha and uses the DECwindows interface.

These products, which are included with the operating system, help
system managers correct system resource utilization problems for CPU
usage, low memory, lock contention, hung or runaway processes, I/O,
disks, page files, and swap files.

Availability Manager enables you to monitor one or more OpenVMS nodes
on an extended LAN from either an OpenVMS Alpha or a Windows node.
Availability Manager collects system and process data from multiple
OpenVMS nodes simultaneously. It analyzes the data and displays the
output using a native Java GUI.

DECamds collects and analyzes data from multiple nodes (VAX and Alpha)
simultaneously, directing all output to a centralized DECwindows
display. DECamds helps you observe and troubleshoot availability
problems, as follows:

It is important to monitor LAN activity on a regular basis. Using the
SCA (Systems Communications Architecture) Control Program (SCACP), you
can monitor LAN activity as well as set and show default ports, start
and stop LAN devices, and assign priority values to channels.

Reference: For more information about SCACP, see the
OpenVMS System Management Utilities Reference Manual: A--L.

Using NCP commands like the following, you can set up a convenient
monitoring procedure to report activity for each 12-hour period. Note
that DECnet event logging for event 0.2 (automatic line counters) must
be enabled.

Reference: For detailed information on DECnet for
OpenVMS event logging, refer to the DECnet for OpenVMS Network Management Utilities manual.

At every timer interval (in this case, 12 hours), DECnet will create an
event that sends counter data to the DECnet event log. If you
experience a performance degradation in your cluster, check the event
log for increases in counter values that exceed normal variations for
your cluster. If all computers show the same increase, there may be a
general problem with your Ethernet configuration. If, on the other
hand, only one computer shows a deviation from usual values, there is
probably a problem with that computer or with its Ethernet interface
device.

The following layered products can be used in conjunction with one of
Compaq's LAN bridges to monitor the LAN traffic levels: RBMS, DECelms,
DECmcc, and LAN Traffic Monitor (LTM).

Some system parameters for Alpha computers are in units of pagelets,
whereas others are in pages. AUTOGEN determines the hardware page size
and records it in the PARAMS.DAT file.

Caution: When reviewing AUTOGEN recommended values or
when setting system parameters with SYSGEN, note carefully which units
are required for each parameter.

Table A-1 describes system parameters that are specific to OpenVMS
Cluster configurations that may require adjustment in certain
configurations. Table A-2 describes OpenVMS Cluster specific system
parameters that are reserved for OpenVMS use.

Reference: System parameters, including cluster and
volume shadowing system parameters, are documented in the
OpenVMS System Management Utilities Reference Manual.

Specifies a numeric value from 0 to 255 to be assigned as the disk
allocation class for the computer. The default value is 0.

CHECK_CLUSTER

Serves as a VAXCLUSTER parameter sanity check. When CHECK_CLUSTER is
set to 1, SYSBOOT outputs a warning message and forces a conversational
boot if it detects the VAXCLUSTER parameter is set to 0.

CLUSTER_CREDITS

Specifies the number of per-connection buffers a node allocates to
receiving VMS$VAXcluster communications.

If the SHOW CLUSTER command displays a high number of credit waits
for the VMS$VAXcluster connection, you might consider increasing the
value of CLUSTER_CREDITS on the other node. However, in large cluster
configurations, setting this value unnecessarily high will consume a
large quantity of nonpaged pool. Each receive buffer is at least
SCSMAXMSG bytes in size but might be substantially larger depending on
the underlying transport.

It is not required that all nodes in the cluster have the same
value for CLUSTER_CREDITS. For small or memory-constrained systems, the
default value of CLUSTER_CREDITS should be adequate.

CWCREPRC_ENABLE

Controls whether an unprivileged user can create a process on another
OpenVMS Cluster node. The default value of 1 allows an unprivileged
user to create a detached process with the same UIC on another node. A
value of 0 requires that a user have DETACH or CMKRNL privilege to
create a process on another node.

DISK_QUORUM

The physical device name, in ASCII, of an optional quorum disk. ASCII
spaces indicate that no quorum disk is being used. DISK_QUORUM must be
defined on one or more cluster computers capable of having a direct
(not MSCP served) connection to the disk. These computers are called
quorum disk watchers. The remaining computers
(computers with a blank value for DISK_QUORUM) recognize the name
defined by the first watcher computer with which they communicate.

++DR_UNIT_BASE

Specifies the base value from which unit numbers for DR devices
(StorageWorks RAID Array 200 Family logical RAID drives) are counted.
DR_UNIT_BASE provides a way for unique RAID device numbers to be
generated. DR devices are numbered starting with the value of
DR_UNIT_BASE and then counting from there. For example, setting
DR_UNIT_BASE to 10 will produce device names such as $1$DRA10,
$1$DRA11, and so on. Setting DR_UNIT_BASE to appropriate,
nonoverlapping values on all cluster members that share the same
(nonzero) allocation class will ensure that no two RAID devices are
given the same name.

EXPECTED_VOTES

Specifies a setting that is used to derive the initial quorum value.
This setting is the sum of all VOTES held by potential cluster members.

By default, the value is 1. The connection manager sets a quorum
value to a number that will prevent cluster partitioning (see
Section 2.3). To calculate quorum, the system uses the following
formula:

estimated quorum = (EXPECTED_VOTES + 2)/2

LOCKDIRWT

Lock manager directory system weight. Determines the portion of lock
manager directory to be handled by this system. The default value is
adequate for most systems.

+LRPSIZE

For VAX computers running VMS Version 5.5--2 and earlier, the LRPSIZE
parameter specifies the size, in bytes, of the large request packets.
The actual physical memory consumed by a large request packet is
LRPSIZE plus overhead for buffer management. Normally, the default
value is adequate. The value of LRPSIZE affects the transfer size used
by VAX nodes on an FDDI ring.

FDDI supports transfers using large packets (up to 4468 bytes).
PEDRIVER does not use large packets by default, but can take advantage
of the larger packet sizes if you increase the LRPSIZE system parameter
to 4474 or higher.

PEDRIVER uses the full FDDI packet size if the LRPSIZE is set to
4474 or higher. However, only FDDI nodes connected to the same ring use
large packets. Nodes connected to an Ethernet segment restrict packet
size to that of an Ethernet packet (1498 bytes).

++MC_SERVICES_P0 (dynamic)

Controls whether other MEMORY CHANNEL nodes in the cluster continue to
run if this node bugchecks or shuts down.

A value of 1 causes other nodes in the MEMORY CHANNEL cluster to
fail with bugcheck code MC_FORCED_CRASH if this node bugchecks or shuts
down.

The default value is 0. A setting of 1 is intended only for
debugging purposes; the parameter should otherwise be left at its
default state.

++MC_SERVICES_P2 (static)

Specifies whether to load the PMDRIVER (PMA0) MEMORY CHANNEL cluster
port driver. PMDRIVER is a new driver that serves as the MEMORY CHANNEL
cluster port driver. It works together with MCDRIVER (the MEMORY
CHANNEL device driver and device interface) to provide MEMORY CHANNEL
clustering. If PMDRIVER is not loaded, cluster connections will not be
made over the MEMORY CHANNEL interconnect.

The default for MC_SERVICES_P2 is 1. This default value causes
PMDRIVER to be loaded when you boot the system.

Compaq recommends that this value not be changed. This parameter
value must be the same on all nodes connected by MEMORY CHANNEL.

++MC_SERVICES_P3 (dynamic)

Specifies the maximum number of tags supported. The maximum value is
2048 and the minimum value is 100.

The default value is 800. Compaq recommends that this value not be
changed.

This parameter value must be the same on all nodes connected by
MEMORY CHANNEL.

++MC_SERVICES_P4 (static)

Specifies the maximum number of regions supported. The maximum value is
4096 and the minimum value is 100.

The default value is 200. Compaq recommends that this value not be
changed.

This parameter value must be the same on all nodes connected by
MEMORY CHANNEL.

++MC_SERVICES_P6 (static)

Specifies MEMORY CHANNEL message size, the body of an entry in a free
queue, or a work queue. The maximum value is 65536 and the minimum
value is 544. The default value is 992, which is suitable in all cases
except systems with highly constrained memory.

For such systems, you can reduce the memory consumption of MEMORY
CHANNEL by slightly reducing the default value of 992. This value must
always be equal to or greater than the result of the following
calculation:

Select the larger of SCS_MAXMSG and SCS_MAXDG.

Round that value to the next quadword.

This parameter value must be the same on all nodes connected by
MEMORY CHANNEL.

++MC_SERVICES_P7 (dynamic)

Specifies whether to suppress or display messages about cluster
activities on this node. Can be set to a value of 0, 1, or 2. The
meanings of these values are:

Value

Meaning

0

Nonverbose mode---no informational messages will appear on the console
or in the error log.

1

Verbose mode---informational messages from both MCDRIVER and PMDRIVER
will appear on the console and in the error log.

2

Same as verbose mode plus PMDRIVER stalling and recovery messages.

The default value is 0. Compaq recommends that this value not be changed except for debugging MEMORY CHANNEL problems or adjusting the MC_SERVICES_P9 parameter.

++MC_SERVICES_P9 (static)

Specifies the number of initial entries in a single channel's free
queue. The maximum value is 2048 and the minimum value is 10.

Note that MC_SERVICES_P9 is not a dynamic parameter; you must
reboot the system after each change in order for the change to take
effect.

The default value is 150. Compaq recommends that this value not be
changed.

This parameter value must be the same on all nodes connected by
MEMORY CHANNEL.

++MPDEV_ENABLE

Enables the formation of multipath sets when set to ON (1). If set to
OFF (0), the formation of additional multipath sets is disabled.
However, existing multipath sets remain in effect. The default is ON.

++MPDEV_LCRETRIES

Controls the number of times the system retries locally connected paths
before moving on to local unconnected paths or to an MSCP served path
to the device. The valid range for retries is 1 through 256. The
default is 1.

++MPDEV_POLLER

Enables polling of the paths to multipath set members when set to ON
(1). Polling allows early detection of errors on inactive paths. If a
path becomes unavailable or returns to service, the system manager is
notified with an OPCOM message. If set to OFF (0), multipath polling is
disabled. The default is ON.

++MPDEV_REMOTE

Enables MSCP served disks to become members of a multipath set when set
to ON (1). If set to OFF (0), only local paths to a SCSI device will be
used in the formation of additional multipath sets. However, existing
remote members of multipath sets remain as members of them. The default
is OFF. For OpenVMS Version 7.2, the only valid setting is OFF.

MSCP_BUFFER

This buffer area is the space used by the server to transfer data
between client systems and local disks.

On VAX systems, MSCP_BUFFER specifies the number of pages to be
allocated to the MSCP server's local buffer area.

On Alpha systems, MSCP_BUFFER specifies the number of pagelets to
be allocated the MSCP server's local buffer area.

MSCP_CMD_TMO

Specifies the time in seconds that the OpenVMS MSCP server uses to
detect MSCP command timeouts. The MSCP server must complete the command
within a built-in time of approximately 40 seconds plus the value of
the MSCP_CMD_TMO parameter.

An MSCP_CMD_TMO value of 0 is normally adequate. A value of 0
provides the same behavior as in previous releases of OpenVMS (which
did not have an MSCP_CMD_TMO system parameter). A nonzero setting
increases the amount of time before an MSCP command times out.

If command timeout errors are being logged on client nodes, setting
the parameter to a nonzero value on OpenVMS servers reduces the number
of errors logged. Increasing the value of this parameter reduces the
numb client MSCP command timeouts and increases the time it takes to
detect faulty devices.

If you need to decrease the number of command timeout errors, set
an initial value of 60. If timeout errors continue to be logged, you
can increase this value in increments of 20 seconds.

MSCP_CREDITS

Specifies the number of outstanding I/O requests that can be active
from one client system.

MSCP_LOAD

Controls whether the MSCP server is loaded. Specify 1 to load the
server, and use the default CPU load rating. A value greater than 1
loads the server and uses this value as a constant load rating. By
default, the value is set to 0 and the server is not loaded.

MSCP_SERVE_ALL

Controls the serving of disks. The settings take effect when the system
boots. You cannot change the settings when the system is running.

Starting with OpenVMS Version 7.2, the serving types are
implemented as a bit mask. To specify the type of serving your system
will perform, locate the type you want in the following table and
specify its value. For some systems, you may want to specify two
serving types, such as serving the system disk and serving locally
attached disks. To specify such a combination, add the values of each
type, and specify the sum.

In a mixed-version cluster that includes any systems running
OpenVMS Version 7.1-
x or earlier, serving all available disks is restricted to
serving all disks except those whose allocation class does not match
the system's node allocation class (pre-Version 7.2 meaning). To
specify this type of serving, use the value 9 (which sets bit 0 and bit
3).

The following table describes the serving type controlled by each
bit and its decimal value.

Bit and Value When Set

Description

Bit 0 (1)

Serve all available disks (locally attached and those connected to HS
x and DSSI controllers). Disks with allocation classes that
differ from the system's allocation class (set by the ALLOCLASS
parameter) are also served if bit 3 is not set.

Bit 1 (2)

Serve locally attached (non-HS
x and non-DSSI) disks.

Bit 2 (4)

Serve the system disk. This is the default setting. This setting is
important when other nodes in the cluster rely on this system being
able to serve its system disk. This setting prevents obscure contention
problems that can occur when a system attempts to complete I/O to a
remote system disk whose system has failed.

Bit 3 (8)

Restrict the serving specified by bit 0. All disks except those with
allocation classes that differ from the system's allocation class (set
by the ALLOCLASS parameter) are served.

This is pre-Version 7.2 behavior. If your cluster includes systems
running Open 7.1-
x or earlier, and you want to serve all available disks, you
must specify 9, the result of setting this bit and bit 0.

Although the serving types are now implemented as a bit mask, the values of 0, 1, and 2, specified by bit 0 and bit 1, retain their original meanings:

0 --- Do not serve any disks (the default for earlier versions of OpenVMS).

1 --- Serve all available disks.

2 --- Serve only locally attached (non-HSx and non-DSSI) disks.

If the MSCP_LOAD system parameter is 0, MSCP_SERVE_ALL is ignored. For more information about this system parameter, see Section 6.3.1.

NISCS_CONV_BOOT

During booting as an OpenVMS Cluster satellite, specifies whether
conversational bootstraps are enabled on the computer. The default
value of 0 specifies that conversational bootstraps are disabled. A
value of 1 enables conversational bootstraps.

NISCS_LAN_OVRHD

Starting with OpenVMS Version 7.3, this parameter is obsolete. This
parameter was formerly provided to reserve space in a LAN packet for
encryption fields applied by external encryption devices. PEDRIVER now
automatically determines the maximum packet size a LAN path can
deliver, including any packet-size reductions required by external
encryption devices.

NISCS_LOAD_PEA0

Specifies whether the port driver (PEDRIVER) is to be loaded to enable
cluster communications over the local area network (LAN). The default
value of 0 specifies that the driver is not loaded. A value of 1
specifies that that driver is loaded.

Caution: If the NISCS_LOAD_PEA0 parameter is set to 1,
the VAXCLUSTER system parameter must be set to 2. This ensures
coordinated access to shared resources in the OpenVMS Cluster and
prevents accidental data corruption.

NISCS_MAX_PKTSZ

Specifies an upper limit, in bytes, on the size of the user data area
in the largest packet sent by NISCA on any local area network (LAN).

The NISCS_MAX_PKTSZ parameter allows the system manager to change
the packet size used for cluster communications on network
communication paths. PEDRIVER automatically allocates memory to support
the largest packet size that is usable by any virtual circuit connected
to the system up to the limit set by this parameter.

Its default values are different for OpenVMS Alpha and OpenVMS VAX.

On Alpha, the default value is the largest packet size currently
supported by OpenVMS, in order to optimize performance.

On VAX, the default value is the Ethernet packet size.

PEDRIVER uses NISCS_MAX_PKTSZ to compute the maximum amount of data
to transmit in any LAN packet as follows:

The actual packet size automatically used by PEDRIVER might be
smaller than the NISCS_MAX_PKTSZ limit for either of the following
reasons:

On a per-LAN-path basis, if PEdriver determines that the LAN path
between two nodes, including the local and remote LAN adapters and
intervening LAN equipment, can convey only a lesser size.

Only nodes with large-packet LAN adapters connected end-to-end by
large-packet LAN equipment can use large packets. Nodes connected to
large-packet LANs but having an end-to-end path that involves an
Ethernet segment restrict packet size to that of an Ethernet packet
(1498 bytes).

For performance reasons, PEDRIVER might further limit the upper
bound on packet size so that the packets can be allocated from a
lookaside list in the nonpaged pool.

The actual memory allocation includes the required data structure
overhead used by PEDRIVER and the LAN drivers, in addition to the
actual LAN packet size.

The following table shows the minimum NISCS_MAX_PKTSZ value
required to use the maximum packet size supported by LAN types.

Type of LAN

Minimum Value for NISCS_MAX_PKTSZ

Ethernet

1498

FDDI

4468

Gigabit Ethernet

7532

ATM

7606

PASTDGBUF

Specifies the number of datagram receive buffers to queue initially for
the cluster port driver's configuration poller. The initial value is
expanded during system operation, if needed.

MEMORY CHANNEL devices ignore this parameter.

QDSKINTERVAL

Specifies, in seconds, the disk quorum polling interval. The maximum is
32767, the minimum is 1, and the default is 3. Lower values trade
increased overhead cost for greater responsiveness.

This parameter should be set to the same value on each cluster
computer.

QDSKVOTES

Specifies the number of votes contributed to the cluster votes total by
a quorum disk. The maximum is 127, the minimum is 0, and the default is
1. This parameter is used only when DISK_QUORUM is defined.

RECNXINTERVAL

Specifies, in seconds, the interval during which the connection manager
attempts to reconnect a broken connection to another computer. If a new
connection cannot be established during this period, the connection is
declared irrevocably broken, and either this computer or the other must
leave the cluster. This parameter trades faster response to certain
types of system failures for the ability to survive transient faults of
increasing duration.

This parameter should be set to the same value on each cluster
computer. This parameter also affects the tolerance of the OpenVMS
Cluster system for LAN bridge failures (see Section 3.4.7).

SCSBUFFCNT

+On VAX systems, SCSBUFFCNT is the number of buffer descriptors
configured for all SCS devices. If no SCS device is configured on your
system, this parameter is ignored. Generally, each data transfer needs
a buffer descriptor: thus, the number of buffer descriptors limit the
number of possible simultaneous I/Os. Various performance monitors
report when a system is out of buffer descriptors for a given work
load, indicating that a larger value for SCSBUFFCNT is worth
considering.

++On Alpha systems, the SCS buffers are allocated as needed, and
SCSBUFFCNT is reserved for OpenVMS use, only.

SCSCONNCNT

The initial number of SCS connections that are configured for use by
all system applications, including the one used by Directory Service
Listen. The initial number will be expanded by the system if needed.

If no SCS ports are configured on your system, this parameter is
ignored. The default value is adequate for all SCS hardware
combinations.

Specify SCSNODE as a string of up to six characters. Enclose the
string in quotation marks.

If the computer is in an OpenVMS Cluster, specify a value that is
unique within the cluster. Do not specify the null string.

If the computer is running DECnet for OpenVMS, the value must be
the same as the DECnet node name.

SCSRESPCNT

SCSRESPCNT is the total number of response descriptor table entries
(RDTEs) configured for use by all system applications.

If no SCS or DSA port is configured on your system, this parameter
is ignored.

SCSSYSTEMID
1

Specifies a number that identifies the computer. This parameter is not
dynamic. SCSSYSTEMID is the low-order 32 bits of the 48-bit system
identification number.

If the computer is in an OpenVMS Cluster, specify a value that is
unique within the cluster.

If the computer is running DECnet for OpenVMS, calculate the value
from the DECnet address using the following formula:

SCSSYSTEMID = (
DECnet-area-number * 1024)
+
DECnet-node-number

Example: If the DECnet address is 2.211, calculate the
value as follows:

SCSSYSTEMID = (2 * 1024) + 211 = 2259

SCSSYSTEMIDH

Specifies the high-order 16 bits of the 48-bit system identification
number. This parameter must be set to 0. It is reserved by OpenVMS for
future use.

TAPE_ALLOCLASS

Specifies a numeric value from 0 to 255 to be assigned as the tape
allocation class for tape devices connected to the computer. The
default value is 0.

TIMVCFAIL

Specifies the time required for a virtual circuit failure to be
detected. Compaq recommends that you use the default value. Compaq
further recommends that you decrease this value only in OpenVMS Cluster
systems of three or fewer CPUs, use the same value on each computer in
the cluster, and use dedicated LAN segments for cluster I/O.

TMSCP_LOAD

Controls whether the TMSCP server is loaded. Specify a value of 1 to
load the server and set all available TMSCP tapes served. By default,
the value is set to 0, and the server is not loaded.

TMSCP_SERVE_ALL

Controls the serving of tapes. The settings take effect when the system
boots. You cannot change the settings when the system is running.

Starting with OpenVMS Version 7.2, the serving types are
implemented as a bit mask. To specify the type of serving your system
will perform, locate the type you want in the following table and
specify its value. For some systems, you may want to specify two
serving types, such as serving all tapes except those whose allocation
class does not match. To specify such a combination, add the values of
each type, and specify the sum.

In a mixed-version cluster that includes any systems running
OpenVMS Version 7.1-
x or earlier, serving all available tapes is restricted to
serving all tapes except those whose allocation class does not match
the system's allocation class (pre-Version 7.2 meaning). To specify
this type of serving, use the value 9, which sets bit 0 and bit 3.

The following table describes the serving type controlled by each
bit and its decimal value.

Bit

Value When Set

Description

Bit 0

1

Serve all available tapes (locally attached and those connected to HS
x and DSSI controllers). Tapes with allocation classes that
differ from the system's allocation class (set by the ALLOCLASS
parameter) are also served if bit 3 is not set.

Bit 1

2

Serve locally attached (non-HS
x and non-DSSI) tapes.

Bit 2

n/a

Reserved.

Bit 3

8

Restrict the serving specified by bit 0. All tapes except those with
allocation classes that differ from the system's allocation class (set
by the ALLOCLASS parameter) are served.

This is pre-Version 7.2 behavior. If your cluster includes systems
running OpenVMS Version 7.1-
x or earlier, and you want to serve all available tapes, you
must specify 9, the result of setting this bit and bit 0.

Although the serving types are now implemented as a bit mask, the values of 0, 1, and 2, specified by bit 0 and bit 1, retain their original meanings:

0 --- Do not serve any disks (the default for earlier versions of OpenVMS).

1 --- Serve all available disks.

2 --- Serve only locally attached (non-HSx and non-DSSI) disks.

If the TMSCP_LOAD system parameter is 0, TMSCP_SERVE_ALL is ignored.

VAXCLUSTER

Controls whether the computer should join or form a cluster. This
parameter accepts the following three values:

0 --- Specifies that the computer will not participate in a cluster.

1 --- Specifies that the computer should participate in a cluster
if hardware supporting SCS (CI or DSSI) is present or if
NISCS_LOAD_PEA0 is set to 1, indicating that cluster communications is
enabled over the local area network (LAN).

2 --- Specifies that the computer should participate in a cluster.

You should always set this parameter to 2 on computers intended to
run in a cluster, to 0 on computers that boot from a UDA disk
controller and are not intended to be part of a cluster, and to 1 (the
default) otherwise.

Caution: If the NISCS_LOAD_PEA0 system parameter is
set to 1, the VAXCLUSTER parameter must be set to 2. This ensures
coordinated access to shared resources in the OpenVMS Cluster system
and prevents accidental data corruption. Data corruption may occur on
shared resources if the NISCS_LOAD_PEA0 parameter is set to 1 and the
VAXCLUSTER parameter is set to 0.

VOTES

Specifies the number of votes toward a quorum to be contributed by the
computer. The default is 1.

+VAX specific
++Alpha specific
1Once a computer has been recognized by another computer in
the cluster, you cannot change the SCSSYSTEMID or SCSNODE parameter
without either changing both or rebooting the entire cluster.